The present invention relates to apparatus and methodology for applying electromagnetic wave energy, particularly microwaves, to a product to be heated, such as contaminated and infectious waste products to be sterilized.
Environmental concerns have motivated a search for waste incineration systems which efficiently incinerate waste materials while decreasing pollutant emissions. The need for such systems is particularly critical for disposal of contaminated and infectious wastes, such as hospital waste. Traditional incineration systems burn waste at relatively low temperatures and tend to emit unacceptably high levels of fly ash and other pollutants.
The use of electromagnetic energy waves, in particular microwaves, to heat materials is well known. One heating apparatus using microwaves is disclosed in U.S. Pat. No. 4,565,670 to Miyazaki. Miyazaki discloses a stationary outer cylinder and a rotatable inner cylinder to form a passage in between the cylinders for the continuous heat treatment of a substance passing through the passage. Material passes from inlet pipe 1 through passage 14 to outlet pipe 2. As the material traverses the path it is exposed to microwaves through waveguides 3 located at the inlet end position, the outlet end position and an intermediate position on the circumferential wall of the outer cylinder 4. By applying microwave radiation from the periphery, Miyazaki requires the application microwaves at multiple locations.
U.S. Pat. No. 4,608,261 to MacKenzie discloses a method and apparatus for producing a puffed foodstuff using a microwave generator 19 mounted within a microwave cavity 16 to apply microwave energy to raw material passing through a tubular conveyance section 17. Like Miyazaki, MacKenzie situates the microwave generator at a point above the material to be radiated.
U.S. Pat. No. 4,330,946 to Courneya discloses a high efficiency material drying apparatus with microwave sources 30 located above a primary chamber 40, where the heat is concentrated on the material moved along an auger pathway. Microwave sources or magnetrons 30 are offset to direct their energy to the location of the majority of material at any instant. Thus, Courneya also has the disadvantage of requiring a plurality of points applying microwaves to the material being heated.
U.S. Pat. No. 4,087,921 discloses a microwave drying apparatus with microwave units 17 located on opposite sides of drum 11 which has longitudinally extending buffers 43 projecting radially inward from the inner surface of the drum. This causes a tumbling action of material passing through the drum to enhance the drying effect produced by the microwave units 17. Again a plurality of microwave application locations is required.
All of the patent documents discussed above require the application of microwaves using one or more microwave sources located at various locations surrounding the material to be heated. As a result, each of the units is costly and inefficient.
U.S. Pat. No. 4,193,448 to Jeambey discloses an apparatus for recovery of petroleum from petroleum impregnated media. The apparatus uses a microwave generator and a guide for directing microwaves to a dispersing chamber for heating the media. A plurality of holes is used for the flow of heated petroleum into the petroleum chamber. In operation, a hole is drilled in a petroleum impregnated media such as rock or shale and the apparatus is inserted into the hole. A drive motor is energized to rotate blades 50 of mixing device 48 causing microwaves to be dispersed from dispersing chamber 28 through the microwave transparent shell portion 46 into the surrounding media. The media is thus heated and the heated petroleum drains into the drilled hole. Shell 16 is moved up and down to facilitate recovery of oil into the chamber 32 through holes 64. Microwaves do not pass through the holes.
U.S. Pat. No. 4,410,553 to McGinty discloses a method and apparatus for cooking particular foodstuffs. The apparatus uses an elongated source of radiant heat, preferably a single resistance electric heater element which emits infrared radiation. Alternatively, multiple bar resistance electric heater elements having an associated concave reflector could be used. McGinty also discloses the use of a helix which can rotate to advance foodstuffs or can be fixed inside a retaining means and rotate therewith. The helix is further disclosed to have a variable pitch with the smallest pitch being in the area where the cooking is conducted for the longest length of time. Neither Jeambey nor McGinty discloses the use of reflected microwaves to provide heating of a material passing from an inlet to an outlet. In addition, none of the references discloses an efficient means for using a single source of microwave radiation to heat a product. Thus, the current art fails to disclose an in-line microwave applicator which can apply microwaves to material to be heated in an efficient manner.